This invention relates generally to the production of solid state material layers, and more particularly relates to techniques for producing relatively thin, free-standing layers of solid state materials such as microelectronic materials.
For a wide range of microelectronic and microfabrication applications there is required one or more free-standing layers of a microelectronic material to be employed, e.g., as a starting structure on which an electronic and/or mechanical system is to be fabricated. For example, conventional microfabrication processes employ one or more free-standing semiconductor substrates or wafers, such as silicon wafers, on which microelectronic and micromechanical systems are fabricated. Such silicon wafers are produced commercially to meet conventional industry standards for, e.g., doping uniformity and thickness.
Increasingly, the characteristics of commercially available microelectronic substrates such as silicon wafers do not correspond with requirements of important microfabrication applications. In particular, the thickness of conventional substrates such as silicon wafers often is substantially greater than that required for a given microfabrication application, with the unneeded wafer thickness adding cost to the overall microfabricated system but providing no corresponding benefit. For example, high-efficiency silicon solar cells can be produced with a silicon thickness of about 50 microns. But conventional 5-inch diameter silicon wafers produced for fabricating solar cells are typically about 180 μm in thickness. This excess thickness in wafer material provides no benefit to the solar cell operation but dominates the overall solar cell microfabrication expense. As this example demonstrates, in general, as advances in important microfabrication processes and systems such as solar cells and photovoltaic systems continue, the expense and limitations of conventional starting materials like commercial silicon wafers are becoming significant factors in determining the successful implementation and cost effectiveness of these evolving technologies.